Climate Change Impact on Lake Abaya Water Level

Abstract

Abstract The present study area is located in Abaya-Chamo basin, in the southern part of the Ethiopian Rift Valley. In this research project climate change impacts on levels of Lake Abaya is assessed by using appropriate techniques and the future lake level is forecasted based on scenario analysis conducted by changing the lake water balance parameters. Available time series data (satellite, hydrographic, climatic, land use- land cover, socio economic, etc.) of the last two decades, in the area is used to determine the baseline, based on which modeling and lake level fluctuation is assessed .The water balance components of Abaya, the amount of runoff, precipitation, evaporation & storage changes, and their annual changes over the 1987-2005 period is systematically analyzed & formulated as a lake level forecast model. The model shows the average yearly inflow from river discharge, unguaged runoff and precipitation which are 750, 691 and 980 mcm, while the average outflow from evaporation is 2009mcm, respectively. The formulated model is applied in order to ascertain the effect of these components in the historic and future lake levels based on the sequences of 1987-2005 hydro-climatic conditions with different applications and assumptions. The assumptions are generally aims to test several different values of the observed hydro-climatic for future conditions. Based on the assumptions considered in the applications past hydro-climatic conditions observed and recorded as evidence and questionnaires taken from community living in study area, model applications 1A (tried to show the effect of river discharge and precipitation in the lake level rise), 2(tried to show the effect of lake evaporation in the lake level change), 4( the effect of precipitation amount on the surface of the lake and runoff from unguaged catchment in the lake level change) and 5(the effect of runoff amount increases by 50% of the present due to land use/land cover change by deforestation and agricultural land in the lake change) are chosen as a good predicator of Abaya lake level fluctuation. From the models it is observed lake level fluctuate mostly due to climatic factors and also man-made processes, precipitation and evaporation causes the major changes and also deforestation and agricultural expansion in the catchment had their own role.